GEOLOGICAL OBSKKVATIONS IN FIJI. 87 



present active volcanoes, letting down the sea door to the east, thus 

 putting fairly deep water between the New Hebritles and the Fiji 

 land-surface. 



(5). " — During all this period of volcanic activity, extensive 

 submarine tuffaceous beds were accumulating above the folded 

 Miocene series; the earlier deposits followed later by varieties of 

 soapstone. No interbeddcd coral limestone was met among these 

 tuflFs." "Capping this series, are the raised coral reefs elevated to 

 heights of over 2000 feet. The oldest of these is referable to a period 

 not earlier than late Pliocene and probably not much later as it has 

 since been intruded by lava from centers now extinct." 



(G). " — The elevatory movements evidenced in these raised reefs 

 is of a see-saw type, greatest in the west and least (probably in many 

 cases a minus quantity) in the east, wdiere 



(7). " — the great recent basic eruptions have taken place." 



Mawson regards "the elevatory tendency" as a "continuance of 

 the tectonic movements so critically developed in Miocene times," 

 but considers certain of the uplifts as the direct outcome of volcanic 

 intrusion. 



It is believed, therefore, that the older folded series of central Viti 

 Leva are the equivalents of Mawson's Miocene folded series of the New 

 Hebrides. The formation of the coastal-plain series of Viti Levu would 

 then be referred to late Pliocene or Pleistocene time. The elevated 

 limestones of the Lau and Yasawa Groups are correlated, from fossil 

 evidence, with the coastal-plain series. The submarine tuff beds of 

 the New Hebrides, as described by Mawson, are very similar to the 

 rocks of central Vanua Levu. The lack of folding in central Vanua 

 Levu probably means that these tuffs are essentially of the same age 

 as the elevated limestones of the Lau Group and late Pleistocene 

 instead of contemporaneous with the Miocene folded beds of Viti Levu. 



As Mawson has stated for the New Hebrides, the elevatory move- 

 ments of the coastal series in Fiji have been of a see-saw type and 

 have continued to very recent times. The series is believed to be 

 essentially conformable throughout, though the uplift of the islands 

 of the Lau Group has continued through a period from late-Pliocene 

 to Recent. Thus the coastal limestones near the mouth of the 

 Singatoka River may be more recent in date of uplift than the Rewa 

 marls, but they belong essentially to the same series. 



The ages of the plutonic rocks of central Viti Levu and of the sedi- 

 ments which they intrude can only be conjectured. The erosion which 

 exposed these rocks was completed before the Miocene depression. 

 They are doubtless at least as old as the early Tertiary. 



